Intravenous catheterisation of foetus and mare in late pregnancy: management and respiratory, circulatory and metabolic effects.

This research paper discusses the procedure and effects of catheterising the uterine and umbilical vessels of pregnant ponies to study foetal metabolism. It notes that the operation had certain transient effects on both the mother and foetus, but overall, both animals recovered well post-surgery.

Research Method

• The researchers carried out intravenous catheterisation on the uterine and umbilical vessels of 12 pregnant ponies with the aim to study foetal metabolism.
• Anesthesia was ensured during surgery through a combination of acepromazine-butorphanol-detomidine, detomidine, and ketamine. It was maintained with halothane in oxygen and nitrous oxide, using mechanical ventilation.

Observations during and after surgery

• During the operation, maternal arterial blood pressure was consistently higher than 70mmHG and arterial oxygen tension stayed over 100mmHg, indicating that the mares were well oxygenated.
• On the other hand, foetuses exhibited signs of hypercapnia (excessive carbon dioxide) and lactic acidaemia (excess lactic acid in the blood), suggesting some metabolic stress.
• Despite these conditions, most blood gases and metabolites for both mother and foetus returned to normal within 24 hours, though foetal plasma lactate decreased at a slower pace.

Adrenocortical Discharge and Cortisol Levels

• The study showed that the maternal adrenocortical discharge during the procedure was less severe than commonly reported, and plasma cortisol dropped to basal levels by 48 hours post-surgery, suggesting a quick recovery.
• Interestingly, the foetal plasma cortisol levels remained low and did not vary during or after surgery. This might imply that the operation did not overly stress the foetus in terms of cortisol production.

Implications of Arterio-Venous Metabolite and Gas Tension Differences

• During the surgery, the difference in arterio-venous metabolite and gas tension across the uterine and umbilical circulations was slightly higher than during recovery, suggesting that uteroplacental perfusion could have been marginally compromised during the procedure.

Post-operative recovery

• Irrespective of these effects, both the mare and the foetus recovered well after the surgery.
• The researchers found that any issues linked to the foetal catheters were not related to the anaesthesia or the surgery, suggesting that catheterisation procedure was safely done.